Ultraviolet light stabilized cellulose ester plastic composition



United States Patent 3,100,716 Patented Aug. 13, 1963 "ice 3,100,716 ULTRAVEGLET LiGiiiT STABHLEZED CELLULOS E ESTER PLASTHI CUMPQSHTEON Charles J. Kibler a d John W. Tamhiyn, Kingsport, Tenn, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Aug. 1, 1961, Ser. No.

3 Claims. (Cl. 106-lt57) This invention relates to a cellulose ester plastic composition stabilized against weathering and particularly the action of ultraviolet light.

Cellulose esters, for example, cellulose acetate, cellulose butyrate, cellulose acetate-butyr-ate and the like, are well-known thermoplastic materials used in a vast number of articles. However, cellulose esters are adversely affected by weathering, particularly by ultraviolet light. Consequently, much investigation of ways and means to stabilize cellulose ester plastics relative to ultraviolet light has been undertaken. Many additives have been suggested by the prior art for incorporation into cellulose ester plastic compositions as ultraviolet light stabilizers. For a variety of reasons none of these additives have been entirely satisfactory. Consequently, there is a need for new cellulose ester plastic compositions wherein the principal component, the cellulose ester, is stabilized relative to ultraviolet light.

An object of this invention is to provide a new cellulose ester plastic composition stabilized against the effects of ultraviolet light.

This object and others are achieved by this invention which is based on our discovery that the reaction product of a Z-hydroxybenzophenone and a manganous salt is an effective ultraviolet light stabilizer for cellulose esters. Although the chemical structure of this reaction product is not known, there is evidence that it is a complex, such as a phenolate. Hence, this reaction product is referred to hereinafter as a manganous complex of a Z-hydroxybenzophenone.

In summary, this invention comprises a plastic composition stabilized relative to ultraviolet light, which comprises a cellulose ester, and at a small but efiective concentration a manganous complex of a 2-hydroxybenzophenone.

The cellulose ester employed as the plastic component of the plastic composition of this invention is an organic acid ester of cellulose. Examples of such an ester are the homogeneous esters such as cellulose acetate, cellulose propionate, cellulose butyrate and the mixed or heterogeneous esters such as cellulose acetate-propionate and cellulose acetate-butyrate. Processes for making such an ester and the named cellulose esters in particular are well known and -need not, therefore, be described herein.

The manganous complex of a 2-hydroxybenzophenone, as just indicated, is the reaction product of a Z-hydroxybenzophenone and a manganous salt. Typical examples of this ultraviolet light stabilizer are:

Manganous complex of Z-hydroxybenzophenone Manganous complex of 2,4-dihydroxybenzophenone Manganous complex of 2,2-dihydroxybenzophenone Manganous complex of 2,4-dihydroxybenzophenone Manganous complex of 2,2,4-trihydroxybenzophenone Manganous complex of 2,2,4,4'-tetrahydroxybenzophenone The manganous complex of this invention is prepared by admixing :a manganous salt with a Z-hydroxybenzophenone preferably at a molar ratio of the manganous radical or ion to the 2-hydroxybenzophenone of at least about 1:2 and preferably in an alkaline, aqueous medium. it is :also preferred that the anion portion of the manganous salt be such that trace concentrations of it in the plastic composition produce no undesirable eliects. Accordingly, it is preferred that the anion portion of the manganous salt be a carboxylic acid residue such as, for example, the acetate, lactate and the like radicals. Upon contact of the manganous salt with the Z-hydroxybenzophenone, the complex forms and precipitates. Preferaiblygl the precipitate is washed well with water and then Concentration of the manganous complex of a Z-hydroxybenzophenone in the plastlc composition of this invention in general depends upon the extent of ultraviolet light stabilization desired. This in turn depends upon many variables, including the end use of the plastic composition. However, for most purposes a concentration of about 0.1-10 weight percent of the plastic composition gives satisfactory results.

The plastic composition of this invention is prepared preferably by roll-compounding the components thereof, which can include not only cellulose organic acid ester and manganous complex of a 2-hydroxyhenzophenone but also other components such as, for example, suitable plasticizers and the like.

This invention is further illustrated by the following example of a specific embodiment thereof. Unless otherwise indicated this invention is not limited to this embodiment.

Example complex of 2,4-dihydroxybenzophenone was prepared as follows. 4.28 grams (0.02 mole) of 2,4- dihydroxybenzophenone was added to a solution of milliliters of water and 0.8 gram (0.02 mole) of sodium hydroxide. A solution resulted. To this solution was admixed a solution of 2.45 grams (0.01 mole) of manganous acetate [Mn(C H O -4H O] and 30 milliliters of water. An olive green precipitate formed. cipitate was separated from the reaction mixture, washed well with water to remove sodium acetate and unreacted materials, and dried.

A plastic composition was prepared by roll-compounding for four minutes parts by weight of a cellulose acetate-butyrate (13 weight percent acetyl and 38 weight percent butyryl content) with 12 parts by weight of dibutylsebacate as aplasticizer and 1 part f the The manganons by weight o manganous complex of 2,4-dihydroxybenzophenone, the parts by weight being weight units. The temperature of the front roll was 270 F. and that of the back roll was 230 F. An ultraviolet light stabilized plastic composition was thereby obtained.

A sheet of this plastic composition, 50 mils thick, was compression molded at 320 F. for 10 minutes and then cut into plates having the dimensions 2.5 inches by 0.5 inch. Measurements were then made on the plates to determine pre-exposure flexural strength and inherent viscosity. These plates were then exposed to artificial weathering in a modified Atlas Twin-Arc Weather-Ometer (Anal. Chem. 25, 460 (1953)).

For purpose of comparison other plastic compositions were prepared in the same manner, formed into sheets and plates by the same procedure, subjected to the same pre-exposure measurements and then placed into the modifled Atlas Twin-Arc Weather-Ometer. Each of these other plastic compositions were by weight of the cellulose acetate-butyrate used in making up the plastic composition of this invention an 12 parts by weight of dibutyl sebacate. One of these plastic compositions contained no ultraviolet light stabilizer at all. The other plastic compositions contained 1 part by weight of the compounds identified in the Stabilizer column of the following table.

The progress of weathering damage to the test plates was followed quantitively by measurements of flexural strength, brittleness and inherent viscosity. Flexural strength Was determined by the Tour-Marshall test for stiffness in flexure (ASTM D747-50), the specimen being Measurement of inherent viscosity (J. Colloid Sci. 1, 261 (1946)) was made at 25C. on a solution of 0.25 gram employed as ultraviolet stabilizers in the plastic compositions were rated on the bases of the following definitions:

unal strength loss is the ratio of the exposure time required to cause 25% loss of fiexural strength in the stabil-- ized composition to the exposure time required to cause 25 loss of fiexural strength in the unstabilized composi- (2) Stabilization rating based on retardation of embrittlement is the ratio of the exposure time for deve1opexposure time for development of brittleness in the unstabilized composition.

(3) Stabilization rating based on retardation of viscosity is the ratio of the exposure time required for 25% loss of inherent viscosity in the stabilized composition to the exposure time for 25% loss of inherent viscosity in the unstabilized composition.

Under these definitions of stabilization ratings, a value of 1.0 indicates no ultraviolet light stabilization while values greater than 1.0 indicate positive degrees of ultraviolet light stabilization.

The following table summarizes the results of this extensive comparative testing:

Stabilization Rating Based on Retardation oi- Thus, the manganous complex of 2,4-dihydroxybenzophenone tin cellulose ester compositions has ultraviolet light stabilization ratings greater than those of chemically related compounds. Hence, there are provided cellulose ester plastic compositions of improved ultraviolet light stability.

ing and under normal use conditions.

Other advantages, features and embodiments of this fications thereof embracing the spirit and essential characteristics of this invention are Within the scope of the claimed subject matter unless expressly excluded by claim language.

We claim:

the group consisting of cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate, and cellulose acetate-butyrate, and (2) an ultraviolet ing of 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2,4-trihydroxybenzophenone and 2,2',4,4'- tetrahydroxybenzophenone.

3. A cellulose ester plastic composition consisting essentially of (1) a cellulose organic acid ester selected from phenone selected from the group consisting of Z-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ',4- trihydroxybenzophenone and 2,2,4,4-tetrahydroxybenzophenone.

References Cited in the file of this patent UNITED STATES PATENTS 2,819,978 Long et a1. Jan. 14, 1958 2,971,921 Coleman et al Feb. 14, 1961 2,974,053 .Sochow Mar. 7, 1961 2,976,259 Hardy etal Mar. 21, 1961 1,008,858 Blake et al. Nov. 14, 1961 

2. A CELLULOSE ESTER PLASTIC COMPOSITION CONSISTING ESSENTIALLLY OF (1) A CELLULOSE ORGANIC ACID ESTER SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ACETATE, CELLULOSE PROPIONATE, CELLULOSE BUTYRATE, CELLULOSE ACETATE-PROPIONATE, AND CELLULOSE ACETATE-BUTYRATE, AND (2) AN ULTRAVIOLET LIGHT STABILIZING QUANTITY OF THE MAGNANOUS COMPLEX OF A 2-HYDROXYBENZOPHENONE SELECTED FROM THE GROUP CONSISTING OF 2-HYDROXYBENZOPHENONE, 2,4-DIHTDROXYBENZOPHENONE, 2,2''-DIHYDROXYBENZOPHENONE, 2,4''-DIHYDROXYBENZOPHENONE, 2,2'',4-TRIHYDROXYBENZOPHENONE AND 2,2'',4,4''TETRAHYDROXYBENZOPHENONE. 